“It’s very possible that humans could hibernate,” says Kelly Drew, a professor at the University of Alaska’s Institute of Arctic Biology. Drew studies arctic ground squirrels, chunky little creatures that disappear into burrows for eight months of the year. When she and I spoke, it was 35 degrees Fahrenheit below zero (without wind chill) at her lab in Fairbanks, at 2:00 in the afternoon (just before sunset). Suddenly my case for hibernation felt trivial.
The essence of hibernation, Drew explains, is body-temperature regulation. Dropping the body’s core temperature induces a low-metabolic state of “torpor,” in which animals require almost no food. Most of the calories we “warm-blooded” animals burn go into maintaining our body temperatures—our basal metabolic rate. The squirrels Drew studies, for example, curl up into little balls and plummet from 99 degrees to 27. This drops their basal metabolic rate by about 99 percent.
Even dwarf lemurs, primates like us, can similarly reduce their caloric needs to 2 percent by dropping their temperatures. Humans unfortunately seem to have a stubbornly fixed set point: 98.6 degrees. Apart from minuscule daily fluctuations like a night-time drop that coincides with sleep, our temperatures only change as an indication of peril—fever or hypothermia. Just a few degrees can mean the difference between health and imminent death.
This set point was long thought to be immutable, but it may not be. Even though humans don’t typically go into torpor of their own volition—and our bodies typically prevent it by shivering—Drew explains that there’s no single “hibernation molecule” or organ that humans lack. In fact, torpor can be induced by doctors in extreme circumstances. Surgeons, for example, use hypothermia during procedures in which the heart must be stopped for a prolonged period—allowing the brain and other organs to survive longer while deprived of fuel. Cooling is also used in emergency cases after cardiac arrest. Covering sedated patients in blankets that circulate cool water is believed to have a similar effect to putting an ice pack on a sprained ankle, decreasing the inflammatory process to minimize lasting damage to the heart and central nervous system.
Cooling is now widely practiced in hospitals, and some doctors have come to believe the principle could be taken further—essentially keeping people alive after they die. At the University of Maryland, the surgeon Samuel Tisherman is studying what he calls “emergency preservation and resuscitation,” or EPR, an experimental protocol in which doctors rapidly cool trauma victims whose heart stops beating. This could buy time for emergency surgery. Right now, in a severe trauma case, a patient may only have a matter of minutes to live—not enough to make it to the operating table. For example, Tisherman describes a person with a gunshot wound to the aorta who’s bleeding internally, very quickly. If that person’s heart stops, Tisherman’s team will surgically open the chest and massage the heart to keep it pumping as they try to repair the aorta. This only takes a few minutes, but when the patient loses too much blood, it’s over. Deprived of oxygen, the brain dies within minutes.